The present invention relates to an apparatus for transferring objects, and more particularly to multiple independent robot assemblies for the simultaneous and independent manipulation of multiple objects, such as semiconductor wafers.
The use of robot arms is a well established manufacturing expedient in applications where human handling is inefficient and/or undesired. For example, in the semiconductor arts robot arms are used to handle wafers during various process steps. Such process steps include those which occur in a reaction chamber, e.g. etching, deposition, passivation, etc., where a sealed environment must be maintained to limit the likelihood of contamination and to ensure that various specific processing conditions are provided.
Current practice includes the use of robot arms to load semiconductor wafers from a loading port into various processing ports within a multiple process chamber system. The robot arms are then employed to retrieve the wafer from a particular port after processing within an associated process chamber. The wafer is then shuttled by the robot arms to a next port for additional processing. When all processing of the wafer within the system is complete, the robot arm returns the semiconductor wafer to the loading port and a next wafer is placed into the system by the robot arm for processing. Typically, a stack of several semiconductor wafers is handled in this manner during each process run, and several wafers are passing through the system simultaneously.
In multiple chamber process systems, it is desirable to have more than one semiconductor wafer in process at a time. In this way, the process system is used to obtain maximum throughput. A typical wafer handling sequence to switch wafers in a process chamber is to remove a wafer from a process chamber, store the wafer in a selected location, pick a new wafer from a storage location, and then place the new wafer in the process chamber. Although this improves use of the system and provides improved throughput, the robot arm itself must go through significant repetitive motion to simply exchange wafers.
To increase the efficiency of robot handling of wafers, a robot arm having the ability to handle two wafers at the same time may be provided. Thus, some equipment manufacturers have provided a robot in which two carrier arms are located at opposed ends of a support, and the support is rotated about a pivot. In this way, one wafer may be stored on one arm while the other arm is used to retrieve and place a second wafer. The arms are then rotated and the stored wafer may be placed as desired. Such a mechanism does not allow the two arms to be present in the same process chamber at the same time, nor does it allow for the immediate replacement of a fresh wafer in a process chamber after a processed wafer is removed, because the support must be rotated 180xc2x0 to place the wafer on the second arm in a position for loading into the location from which the first wafer was removed. Likewise, simultaneous use of the two arms for placement or removal of wafers from process or storage positions is not possible with this configuration.
Another robot configuration includes a central hub having two opposed arms, each arm arranged for rotation relative to the hub while arcuately fixed in relation to one another. A blade is linked to the free ends of the arms, and a drive is provided for rotating the arms in opposite directions from each other to extend the blade radially from the central hub, and in the same direction to effect a circular movement of the blade about the central hub. Preferably, a second pair of arms extend opposed from the first pair, on the ends of which is connected a second blade. Opposed rotation of the arms in one direction extends the first arm while retracting the second arm. Opposed rotation of the arms in the opposite direction results in retraction of the first arm and extension of the second arm. Simultaneous motion of the arms in the same direction swings the blades in a circular or orbital path around the hub. The use of two blades increases throughput. However, this device still does not permit simultaneous insertion of a fresh wafer into a process chamber as a processed wafer is being withdrawn from the same chamber, or independent use of the blades to simultaneous load into wafers, unload from, wafers or move a wafer between one or more chambers while a second wafer is being loaded or unloaded.
The present invention is a multiple robot assembly including at least coaxial upper and lower robot assemblies. The upper robot operates independently of the lower robot to obtain improved throughput and increased wafer handling capacity of the robot assembly as compared to the prior art opposed dual blade robots. The upper robot may be stacked above the lower robot and the two robots may be mounted concentrically to allow fast wafer transfer. Each robot can be either a single blade robot or a dual blade robot.
According to one aspect of the invention, each of the upper and lower robot assemblies is a dual blade robot including a pair of extendable arm assemblies located within a transfer chamber. Each pair of extendable arm assemblies includes a corresponding pair of carrier blades for handling various objects, such as semiconductor wafers. The upper robot may be provided with a drive mechanism for rotating the pair of extendable arm assemblies or for extending one of the arm assemblies into an adjacent chamber. The lower robot may also be provided with a drive mechanism that is coaxial with the upper robot drive mechanism. The lower robot drive mechanism may also function to either rotate the pair of extendable arm assemblies or to extend one of the arm assemblies into an adjacent chamber.
According to another aspect of the invention, each of the upper and lower robot assemblies is a single blade robot including an extendable arm assembly located within a transfer chamber. Each extendable arm assembly includes a corresponding carrier blade for handling various objects, such as semiconductor wafers. The upper and lower robot assemblies may be provided with a drive mechanism for rotating the extendable arm assembly or for extending their arm assemblies into an adjacent chamber.
In a further aspect of the invention, a central transfer chamber is linked to multiple object rest positions, and each of the rest positions may be independently and, if desired, simultaneously accessed by at least two robot assemblies.
A still further aspect of the present invention is an apparatus for holding a plurality of articles within a chamber, such as a pre-process chamber, process chamber or post-process chamber, with a pedestal centrally located and vertically movable therein. The apparatus exhibits a wafer lifting and storing apparatus including a plurality of vertically movable lift pins surrounding the pedestal. The lift pins are configured to receive and hold a plurality of stacked wafers, preferably two, therein. Each one of the plurality of lift pins preferably comprises a lower lift pin segment exhibiting a lower wafer support surface proximal to the upper end thereof, and an upper life pin segment hingedly connected to the lower lift pin segment and exhibiting an upper wafer support surface proximal to an upper end thereof. Means for moving the upper lift pin segment between a position in which the lower lift pin segment is exposed and a position wherein the lower lift pin segment is covered by the upper lift pin segment may also be provided.